Epson salts for magnesium deficiency in tomatoes

You want half an ounce per pint of water. Mix into warm water to make sure it dissolves well then allow to cool.
Spray the leaves with it as well as watering the plant. Even if you are not sure the problem is magnesium deficiency, try it because it can do no harm.

Thanks John your reply was VERY MUCH appreciated. Now going to do as you advised

You're very welcome - best of luck with everything